Wireless LANs are gaining substantial acceptance as a means for providing connectivity over a restricted area to mobile devices. Whilst there are a number of different wireless LAN architectures and the present invention is not limited to any particular one (or, indeed to wireless LANs), the following description is generally written using the terminology applied in the ANSI/IEEE Standard 802.11 (“Wireless LAN Medium Access Control and Physical Layer Specifications”). More particularly, FIG. 1 of the accompanying drawings illustrates the main components of a wireless LAN using that terminology. Thus, a typical wireless LAN 5 comprises a distribution system 10 that serves to interconnect a number of access points (AP) 11 via a network. Each access point 11 connects with mobile stations (MS) 12 over a wireless medium to form a Basic Service Set 13 (BSS1 and BSS2). The totality of the basis service sets and the network that interconnects them is called an Extended Service Set (ESS). The wireless LAN may connect with other networks via a portal 14.
Wireless LANs can be used to provide connectivity over limited areas such as public spaces and publicly-accessible premises, both commercial and non-commercial. These limited areas of connectivity are often referred to as “hotspots” as they generally provide a much higher speed of data transfer to mobile devices than is available via other wireless systems of more general coverage such as the data-capable bearer services provided by cellular radio networks such as GSM.
Whilst such connectivity “hotspots” are presently provided primarily by wireless LANs, other technologies can also be used to provide localised areas of high transfer rates (as compared to the surrounding environment) and as used herein the term “hotspot” is intended to be technology independent, merely indicating that improved data transfer rates are available in localised areas. An example of an alternative technology that can be used to provide a communications hotspot is a system that tracks the movement of a mobile device whilst within a limited range and uses a directional antenna pointing at the device to provide a high data rate link. Another example is the use of a cluster of infrared transceivers within a limited area, adjacent transceivers operating at different frequencies or with different modulations to avoid interference.
A significant drawback to the use of communication hotspots for effecting tasks that require a mobile device to communicate with a remote entity (such as file transfer) is that the mobile entity may move out of the coverage area of the hotspot before the task-related communication is completed.